Absorbent article with fluid impermeable backsheet portion beneath main absorption area and method of producing

ABSTRACT

The invention relates to an absorbent product with a longitudinal direction and a transverse direction, two side edges ( 109, 110 ) extending essentially in the longitudinal direction, a front portion ( 114 ), a rear portion ( 115 ), a first surface and a second surface, and an absorption body ( 105 ) arranged between the first surface and the second surface. The absorption body ( 105 ) has a liquid storage area ( 106 ), and a secondary absorption area ( 107 ), the secondary absorption area ( 107 ) comprising portions which completely surround the liquid storage area ( 106 ) in the plane of the product, the liquid storage area ( 106 ) accounting for at least 75% of the total absorption capacity of the product, and a liquid-impermeable material layer ( 104 ) being arranged on the second surface of the product and essentially only within the liquid storage area. 
     The invention also relates to a method of producing the absorbent product.

TECHNICAL FIELD

The invention relates to an absorbent product such as a sanitary towel,a panty liner or an incontinence pad with a longitudinal direction and atransverse direction, two side edges extending essentially in thelongitudinal direction, a front portion, a rear portion, a first surfaceand a second surface, and an absorption body arranged between the firstsurface and the second surface. The invention also comprises a method ofproducing such a product.

BACKGROUND ART

Absorbent products of the type referred to in the introduction are inmost cases provided with a liquid-blocking rear-side layer, usually athin liquidtight plastic film layer. An associated problem, however, isthat the products feel moist and uncomfortable to wear. The moisture canalso cause inconvenience in the form of unpleasant odour and skinirritation. It has therefore become more usual to provide absorbentproducts with breathable liquid-blocking layers, for example microporousplastic films, or impermeable nonwoven materials. Examples of breathablematerials are given in EP 813 848, EP 813 849, EP 710 472, EP 25 315 andU.S. Pat. No. 4,713,069. Such breathable barrier layers do not, however,have an adequate liquid-blocking effect and are therefore in practiceused virtually exclusively in panty liners, where the quantity of liquidabsorbed is very small. Sanitary towels and incontinence pads, which areexpected to absorb considerably greater quantities of liquid, thereforecontinue to be provided with completely liquidtight barrier layers.There is consequently still a need for improved breathability inabsorbent products such as sanitary towels, panty liners andincontinence pads.

Absorbent products such as sanitary towels, panty liners andincontinence pads are intended to be worn in close contact with the bodyof the wearer. In this connection, such an absorbent product is usuallyarranged inside the briefs of the wearer and is kept in contact with thebody during use by pressure from the briefs. However, it has become muchmore common for women to wear what are known as thongs, that is to saybriefs in which the rear part of the crotch portion is very narrow. Inthis connection, sanitary towels, panty liners and incontinence padswhich are designed to fit in conventional briefs have proved to bevirtually impossible to fasten in a thong in such a manner that thetowel or the panty liner sits correctly in relation to the body of thewearer and is held in position throughout use. Furthermore, thongs areoften worn for aesthetic reasons because they are virtually invisibleeven under clinging clothes and. do not give rise to unsightly edgelines or creases in the clothes. With a conventional absorbent product,which projects beyond the edges of the thong, a large part of thedesired aesthetic effect of wearing a thong is of course lost. Absorbentproducts have therefore been produced, which are adapted to the shape ofa thong. Such absorbent products are described in SE 9803981-1, WO97/39713 and SE 9901758-4. However, the special essentially triangularshape with a very narrow rear portion, which is necessary in order thata product can fit in a thong, means that the surface area available forabsorption is relatively small. The risk of leakage is then great if theproduct cannot catch and absorb all the bodily fluid discharged.

One object of the invention is therefore to provide a breathableabsorbent product with an improved liquid-absorption capacity. Anotherobject of the invention is to provide a breathable absorbent productwith a high degree of leakproofness. A further object of the inventionis to provide a breathable absorbent product which is suitable for usewith a thong.

DISCLOSURE OF INVENTION

By means of the present invention, an absorbent product of the typementioned in the introduction has been produced, which productessentially eliminates the difficulties mentioned above. A productaccording to the invention is characterized mainly in that theabsorption body has a liquid storage area, and a secondary absorptionarea, the secondary absorption area comprising portions which completelysurround the liquid storage area in the plane of the product, the liquidstorage area accounting for at least 75% of the total absorptioncapacity of the product, and a liquid-impermeable material layer beingarranged on the second surface of the product and essentially onlywithin the liquid storage area.

By concentrating the absorption capacity in a primary liquid absorptionarea where liquid can be absorbed and stored, it is possible to limitand control the spread of liquid in the absorbent product. As a result,it is also possible to limit the extent of the liquidtight barrier layerof the product to this area because other parts of the product areexpected to absorb only extremely small quantities of liquid.

It is advantageous if the liquid storage area consists essentially of amore fine-capillary and/or more hydrophilic material than the secondaryabsorption area, or if the liquid storage area comprisessuperabsorbents, because this means that liquid will be transported inthe direction from the secondary absorption area to the liquid storagearea and not in the opposite direction. As a result, the edges of theliquid storage area also function as liquid transport barriers, so thatliquid will not pass from the liquid storage area to the fluffier and/orless hydrophilic secondary absorption area until the liquid storage areais saturated with liquid.

It has been found that absorbent products worn with thongs stay in placesurprisingly well and it is therefore to a great extent possible topredict where wetting and absorption will take place. The presentinvention exploits this fact to produce a central liquid absorption areawith, in relation to the rest of the product, a great absorptioncapacity and a high degree of leakproofness.

According to one embodiment of the invention, the absorbent product isof essentially triangular plane shape, with a narrower rear portion thanfront portion. Such a shape makes the product particularly suitable foruse together with a thong.

The absorbent product can also be provided with a liquid-permeablerear-side layer which is arranged on the second surface of the product,that is to say the surface intended to face the underwear of the wearerduring use of the product. In this connection, the liquid-impermeablematerial layer is arranged between the liquid storage area of theabsorption body and the liquid-permeable rear-side layer. Such aliquid-permeable rear-side layer suitably comprises a nonwoven layerwhich gives the outside of the product a textile nature. A textile rearside on the product has a number of advantages, such as great comfort,good friction and thus better retention in the underwear, and anattractive appearance.

According to one embodiment of the invention, the, liquid-impermeablematerial layer is connected to the liquid storage area of the absorptionbody on that surface of the liquid storage area which is intended toface away from the wearer when the product is in use. Such an embodimentmakes it possible to handle the combination of liquid storage materialand barrier layer as a single component in a production process.

The liquid storage area should have a great absorption capacity and agood capacity for spreading and storing liquid. In this connection, itis advantageous if the liquid storage area comprises a layer ofcellulose fibres with a density of at least 150 g/m³ and preferably alayer suitably of dry-formed cellulose fibres with a density of at least250 g/m³.

A material which has been found to be suitable for the secondaryabsorption area comprises a layer of bound cellulose-fibre-basedmaterial with a density of at most 125 g/m³ which is arranged on thefirst surface of the product and extends over the liquid storage areaand beyond the edges of the liquid storage area around the entireperiphery of the liquid storage area. Alternatively, the secondaryabsorption material is arranged only around the periphery of the liquidstorage area. In this context, a bound material means a material whichhas been treated with a binder so as to stabilize the fibrous structurein the layer. Accordingly, the material can be bound using latex and/orbinding fibres.

According to one embodiment. of the invention, the rear-side materialconsists of a breathable material with a great capacity to resist liquidpenetration.

According to another embodiment, the liquid storage area has anabsorption capacity accounting for at least 85% of the total absorptioncapacity of the product.

The product can also have an adhesive fastening means which is arrangedon the rear-side material and allows the passage of gas and water vapourwithin the area of the secondary absorption area.

The invention also comprises a method of producing an absorbent productaccording to Patent Claim 1. The method comprises a continuous web ofabsorbent material being laminated by a first surface to a liquidtightmaterial layer, after which liquid storage areas are clipped or cut fromthe laminate of absorbent material and liquidtight material, and acontinuous web of secondary absorption material being joined to a secondsurface of the punched-out liquid storage areas so that these arecompletely surrounded by the secondary absorption material in the planeof the material web, after which absorbent products are clipped or cutfrom the finished laminate.

According to one embodiment of the invention, a covering ofliquid-permeable material is fastened to at least one surface on thelaminate of secondary absorption material and liquid storage areasbefore the absorbent products are cut out of the finished laminate.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in greater detail below with reference to theexemplary embodiments shown in the appended drawings, in which

FIG. 1 shows a sanitary towel according to a first embodiment of theinvention;

FIG. 2 shows a section along the line II—II through the sanitary towelin FIG. 1,

FIG. 3 shows a sanitary towel according to a second embodiment of theinvention, and

FIG. 4 shows a section along the line IV—IV through the sanitary towelin FIG. 3.

MODE(S) FOR CARRYING OUT THE INVENTION

The sanitary towel 101 shown in FIGS. 1 and 2 comprises aliquid-permeable surface layer 102 arranged on that side of the sanitarytowel which is intended to face a wearer during use, a liquid-permeablerear-side layer 103 arranged on that side of the sanitary towel which isintended to face away from the wearer during use, and an absorption body105 enclosed between the two surface layers 102, 103. A liquid barrierlayer 104 is also arranged between the absorption body and the rear-sidelayer 103.

The liquid-permeable surface layer 102 is the same shape and size as theabsorption body 105. The rear-side layer 103 is also shaped like theabsorption body. The surface layers 102, 103 are connected to theabsorption body 105, for example by gluing, needling, sewing, or bywelding using heat or ultrasound.

The liquid-permeable surface layer 102 is of conventional type and cantherefore consist of any liquid-permeable material suitable for thepurpose. Examples of such material are different types of thin nonwovenmaterial, perforated plastic films, net material, liquid-permeable foammaterial or the like. The liquid-permeable surface layer 102 can beconstructed from two or more different materials in order to providedifferent functions of the surface layer. For example, it is usual toarrange a liquid-transporting layer inside a liquid-admission layer. Itis also known to arrange different types of material on different partsof that surface on the sanitary towel which faces the wearer during use.A material with good admission capacity can therefore advantageously bearranged in that portion of the sanitary towel which is expected to bemoistened first by the major part of the bodily fluid, while portions ofthe surface layer which are in the first instance to constitute acontact surface against the body of the wearer are provided with amaterial which has been optimized with regard to softness and kindnessto the skin.

It is not necessary either for the invention that the liquid-permeablesurface layer 102 consists of a separate material layer, but the surfacelayer 102 can be a surface on the absorption body 105 of the sanitarytowel 101.

The liquid-permeable rear-side layer 103 can also consist of anysuitable liquid-permeable material. Particularly advantageous materialsare soft nonwoven materials which provide a soft skin-friendly textilesurface. The use of a textile surface material affords a number ofadvantages, such as a high degree of wearer comfort, high friction andthus better retention in a pair of briefs, and an aestheticallyattractive appearance.

The liquid barrier layer 104 is a layer of liquidtight material.Examples of such material layers are thin plastic films and coatings ofresin, wax, liquidtight adhesive or the like.

The absorption body 105 consists of two parts, a first part whichconstitutes the liquid storage area 106 of the absorption body 105, anda second part which is relatively thin and is in the form of one or morematerial layers which extend over essentially the entire surface of thesanitary towel. During use of the sanitary towel 101, it is arranged inthe genital area of the wearer, with a portion located in the region ofthe vaginal orifice of the wearer. As a result, discharged bodily fluidwill meet the sanitary towel 101 within a limited and to a great extentpredetermined area on the sanitary towel, what is known as the wettingarea. The positioning of the liquid storage area 106 is selected in sucha manner that it coincides with the anticipated wetting area of thesanitary towel 101. The liquid storage area 106 is thereforeconsiderably smaller in area than the sanitary towel as a whole. Byvirtue of the fact that the liquid storage area 106 is positioned in thewetting area of the sanitary towel, however, essentially all the bodilyfluid discharged into the sanitary towel will still pass into and beabsorbed in the liquid storage area 106. It is therefore of utmostimportance that the liquid storage area 106 has sufficient absorptioncapacity to be capable of absorbing the expected quantity of bodilyfluid. In this connection, the absorption capacity in the liquid storagearea 106 is to be at least 75%, and preferably at least 85%, of thetotal absorption capacity of the sanitary towel. It is usually estimatedthat a panty liner should have an absorption capacity of roughly 3-5 mland a sanitary towel should be capable of absorbing roughly 12-15 ml.For products intended for night use, for example, or for incontinencepads, an even greater absorption capacity may be desirable.

The second part of the absorption body 105 is arranged as a layerbetween the liquid-permeable surface layer 102 and the liquid storagearea 106 and serves as a liquid-transfer layer between theliquid-permeable surface layer 102 and the first part of the absorptionbody in the liquid storage area 106. The second part of the absorptionbody 105 also extends beyond the edges of the liquid storage area 106 inthe plane of the product, around the entire periphery of the liquidstorage area 106, and then constitutes a secondary absorption area 107around the liquid storage area 106.

Suitable absorbent materials for use in the absorption body 105 are, forexample, cellulose fluff pulp, absorbent bound fibre layers, tissuelayers, absorbent foam, peat or the like. The absorption body can alsocontain superabsorbent polymers, that is to say polymers with thecapacity to absorb several times their own weight of liquid, forming aliquid-containing gel. Superabsorbents are usually in the form ofparticles, flakes, fibres, granules or the like. The superabsorbentmaterial can be used on its own or together with other absorbentmaterial.

The materials in the liquid storage area 106 and, respectively, thesecondary absorption area 107 are advantageously selected in such amanner that the liquid storage area is more fine-capillary and/or hasgreater hydrophilicity than the secondary absorption area 107. Afine-capillary material can be produced by, for example, compressing aporous, compressible structure, such as a fibre wadding, or by selectinga material with small pores. Generally, it can be said that fibrousstructures with a large proportion of thin fibres have finer capillariesthan fibrous structures with a large proportion of thick fibres. It isalso possible to use what are known as capillary fibres, that is to sayfibres with external capillaries, in order to produce a highly capillarymaterial. In a corresponding manner, a difference in hydrophilicity canbe obtained either by treating the material chemically or physically orby selecting materials which have different hydrophilicity from theoutset.

In order to achieve the desired effect of rapid liquid admission to theliquid storage area 106, great absorption capacity and liquid-retainingcapacity in the liquid storage area 106, as well as little or no spreadof absorbed liquid to the secondary absorption area 107, it is thereforesuitable for the liquid storage area 106 to comprise hydrophilicmaterial with a great absorption capacity, such as cellulose fibres,superabsorbent material or the like, while, the material in thesecondary absorption area 107 can be selected from materials with a low,or very low absorption capacity, for example fibre wadding made ofsynthetic fibres. A material which has been found to functionparticularly well as absorption material in the liquid storage area isthe dry-formed cellulose fibrous material described in WO 94/10956. Amaterial which has proved to function particularly well as secondaryabsorption material is a bulky airlaid latex-bound cellulose-fibre-basedmaterial with a density of at most 125 g/m³.

As mentioned, the secondary absorption area 107 surrounds the liquidstorage area 106 around its entire periphery. As a result, the secondaryabsorption area 107 forms a safety zone which can catch and absorb smallquantities of liquid, or individual drops of liquid, which meet thesanitary towel outside the wetting area. Owing to its lowliquid-transport capacity, the secondary absorption area 107 alsoprevents liquid reaching the edges of the sanitary towel and causingleakage. As the liquid storage area 106 has to have a great absorptioncapacity in relation to its area, this area usually has relatively greatrigidity. The secondary absorption area 107 then serves the additionalpurpose of constituting a soft cushioning between the liquid storagearea 106 and the body of the wearer.

It may also be suitable to make liquid transport in the plane of thesanitary towel even more difficult by providing the sanitary towel withsome form of liquid barrier which prevents liquid being transported inthe absorption material or in the liquid-permeable surface layer 102 tothe very edges of the sanitary towel. Examples of such liquid barriersare compressions, welds, strands of adhesive, folded-over plastic stripsor means of rendering materials hydrophobic, such as wax or the like. Inthis connection, the liquid barriers can be arranged along the edges ofthe sanitary towel and/or along the edges on the liquid storage area106.

The sanitary towel 101 is designed with a relatively wide front portion114 and a considerably narrower rear portion 115. The sanitary towel 101also has two side edges 109, 110, the main extent of which is in thelongitudinal direction of the sanitary towel, and an essentiallytransverse front edge 111 and a likewise transverse rear edge 112.

During use of the sanitary towel 101, the front portion 114 is that partof the sanitary towel which faces forwards on the wearer and will thenbe arranged over the genitals of the wearer. The front portion 114narrows in the direction towards the rear portion 115 which isconsiderably narrower than the front portion 114.

In order that the sanitary towel does not extend so far back during usethat it is conspicuous when it is worn together with a thong, it issuitable for the rear portion of the sanitary towel to have a length ofbetween 80 mm and 140 mm and for the total length of the sanitary towelnot to exceed roughly 260 mm.

In order to fasten the sanitary towel in a pair of briefs, a fasteningmeans 116 is arranged on the outside of the rear-side layer 103 of thesanitary towel. The fastening means 116 is in the form of longitudinalstrips of self-adhesive glue. Before use, the fastening means 116 isprotected in a conventional manner, for example by being covered by aprotective layer of paper or plastic treated with silicone or stamped soas to be easily detachable from the adhesive when the sanitary towel isto be used. The adhesive can of course be arranged in any patternsuitable for the purpose. In order to minimize the effect of theadhesive on the breathability of the sanitary towel within the secondaryabsorption area, it is suitable for as little adhesive as possible to bearranged within this area, or for the adhesive to be arranged in adiscontinuous pattern which allows intermediate, exposed portions of therear-side layer 103 to breathe. Alternatively, a breathable fasteningadhesive can be used, at least within the secondary absorption area 107.Other types of fastening means can also be used, such as frictioncoatings, press-studs, clips, fastening flaps or the like. Anotheralternative is fastening adhesive which is attached to the body of thewearer. Different types of fastening arrangements can also be combinedwith one another. It is common, for example, to provide a sanitary towelwith both fastening adhesive on the rear-side layer and with fasteningflaps.

The sanitary towel 101 shown in FIGS. 1 and 2 can be producedefficiently and economically from continuous material webs by laminatingan absorbent material layer to a liquidtight barrier layer, after whichliquid storage areas with the associated liquid barrier layer areclipped or cut out of the laminate web and joined to the othercomponents of the sanitary towel.

FIGS. 3 and 4 show a sanitary towel 301 comprising a liquid-permeablesurface layer 302, a rear-side layer 303 and an absorption body 305enclosed between the surface layers 302, 303. The surface layers 302,303 are interconnected within an edge portion 317 projecting around theabsorption body 305. Such an edge join can be produced in a conventionalmanner by gluing, sewing, or welding using heat or ultrasound.

The liquid-permeable surface layer 302 can, as described in connectionwith FIGS. 1 and 2, consist of any liquid-permeable material suitablefor the purpose.

The rear-side layer 303 consists of a layer of liquidtight material.Examples of such materials are different types of thin plastic films, ornonwoven material treated so as to resist liquid penetration, forexample by coating with plastic, wax or the like. The liquidtightrear-side layer 303 can also consist of a liquidtight surface on theabsorption body 305. In such an embodiment, however, the rear-side layercannot be joined to the liquid-permeable surface layer 302 in an edgejoin around the absorption body 305, but the sanitary towel 301 then hasa construction similar to that described in connection with the sanitarytowel 101 in FIGS. 1 and 2.

In the embodiment shown in FIG. 4a, the absorption body 305 has the sameconstruction as the absorption body 105 shown in FIGS. 1 and 2. Theabsorption body 305 therefore comprises a liquid storage area 306, and asecondary absorption area 307, the secondary absorption area beingarranged in the form of a material layer which also extends between theliquid-permeable surface layer 302 and the liquid storage area 306. FIG.4b shows an alternative embodiment in which the secondary absorptionarea is arranged only in the same plane as the liquid storage area 306and completely surrounds the liquid storage area in the plane.

Although the absorption body 305 in the figures is shown as beingconstructed from two separate parts, it is possible to make theabsorption body 305 from a single absorption layer which is impartedgreater hydrophilicity and/or more compact structure within the liquidstorage area 306. Greater absorption capacity within the liquid storagearea 306 can also be brought about by means of an accumulation ofabsorption material within this area and/or addition of superabsorbents.

In order to make the sanitary towel 301 breathable within those portionsof the secondary absorption area 307 located around the periphery of theliquid storage area 306, these have been provided with perforations 318which, in FIGS. 4a and 4 b, extend through the entire thickness of thesanitary towel. Alternatively, the perforations 318 can be arrangedthrough only a part of the thickness of the sanitary towel 301 as longas at least the liquidtight rear-side layer 303 is perforated. In thisconnection, the perforations 318 can be produced by, for example,needling, stamping, punching or the like. By perforating a border aroundthe liquid storage area 306, a sanitary towel is therefore obtained witha central liquidtight absorption portion and a surrounding breathablesafety zone.

Like the sanitary towel 101 in FIGS. 1 and 2, the sanitary towel shownin FIGS. 3 and 4 is provided with fastening means in the form of strands316 of adhesive arranged on the liquidtight rear-side layer 303.

Although the invention is described above in connection with sanitarytowels, it can of course also be applied to absorbent products such asincontinence pads and panty liners.

What is claimed is:
 1. An absorbent product with a longitudinaldirection and a transverse direction, two side edges extendingessentially in the longitudinal direction, a front portion, a rearportion, a first surface and a second surface, and an absorption bodyarranged between the first surface and the second surface, theabsorption body has a liquid storage area, and a secondary absorptionarea, the secondary absorption area comprising portions which completelysurround the liquid storage area in the plane of the product, the liquidstorage area accounting for at least 75% of the total absorptioncapacity of the product, and a liquid-impermeable material layer beingarranged on the second surface of the product and essentially onlywithin the liquid storage area.
 2. Absorbent product according to claim1, wherein the product is of essentially triangular plane shape, with anarrower rear portion than front portion.
 3. Absorbent product accordingto claim 1, wherein a liquid-permeable rear-side layer is arranged onthe second surface of the product, the liquid-impermeable material layerbeing arranged between the liquid storage area of the absorption bodyand the liquid-permeable rear-side layer.
 4. Absorbent product accordingto claim 3, wherein the liquid-permeable rear-side layer comprises anonwoven layer.
 5. Absorbent product according to claim 1, wherein theliquid-impermeable material layer is connected to the liquid storagearea of the absorption body.
 6. Absorbent product according to claim 1,wherein the liquid storage area comprises a layer of dry-formedcellulose fibers with a density of at least 250 g/m³.
 7. Absorbentproduct according to claim 1, wherein the secondary absorption areacomprises a layer of bound cellulose-fibre-based material with a densityof at most 125 g/m³ which is arranged on the first surface of theproduct and extends over the liquid storage area and beyond the edges ofthe liquid storage area around the entire periphery of the liquidstorage area.
 8. Absorbent product according to claim 3, wherein therear-side material consists of a breathable material with a greatcapacity to resist liquid penetration.
 9. Absorbent product according toclaim 1, wherein the liquid storage area has an absorption capacityaccounting for 85% of the total absorption capacity of the product. 10.Absorbent product according to claim 1, wherein an adhesive fasteningmeans is arranged on the rear-side material and allows the passage ofgas and water vapor within the area of the secondary absorption area.11. A method of producing an absorbent product, wherein the methodcomprises laminating a first surface of a continuous web of absorbentmaterial to a liquidtight material layer, after which clipping orcutting liquid storage areas from the laminate of absorbent material andliquidtight material, and joining a continuous web of secondaryabsorption material to a second surface of the clipped out or cut outliquid storage areas so that these are completely surrounded by thesecondary absorption material in the plane of the material web, afterwhich clipping or cutting absorbent products from the finished laminate.12. Method according to claim 11, wherein a covering of liquid-permeablematerial is fastened to at least one surface on the laminate ofsecondary absorption material and liquid storage areas before theabsorbent products are cut out of the finished laminate.